Disk drives using various kinds of disks, such as optical disks, magneto-optical disks, flexible magnetic-recording disks, and similar disks for data-storage are known in the art. In particular, hard-disk drives (HDDs) have been widely used as data-storage devices that have proven to be indispensable for contemporary computer systems. Moreover, HDDs have found widespread application to motion picture recording and reproducing apparatuses, car navigation systems, cellular phones, and similar devices, in addition to computers, due to their outstanding information-storage characteristics.
Magnetic-recording disks used in HDDs have multiple concentric data tracks and servo tracks. Each servo track includes a plurality of servo-data patterns containing address information. Each data track includes multiple data sectors containing user data recorded thereon. Data sectors are recorded between the servo data located at discrete locations along the circumferential direction of a track. A magnetic-recording head incorporated in head-slider supported by a rotary actuator accesses a desired data sector of a track determined by address information contained in the servo data to write data to, or alternatively, to read data from, the data sector.
To increase the recording density of a magnetic-recording disk, the clearance, which is identified with the term of art, “fly-height,” between the magnetic-recording head flying over the magnetic-recording disk and the magnetic-recording disk has been progressively decreasing. Moreover, magnetic-recording technology continues to develop procedures both to control the clearance, and to suppress variations in the clearance. One such procedure, referred to by the term of art, “thermal fly-height control” (TFC), utilizes a heater in the head-slider to adjust the clearance. TFC generates heat through Joule heating to make the magnetic-recording head protrude in response to thermal expansion of the head-slider. Protrusion decreases the clearance between the magnetic-recording disk and the magnetic-recording head. Other procedures are also known in the art, for example, procedures that use a piezo element, or Coulomb force, to adjust the clearance between the magnetic-recording disk and the magnetic-recording head. Engineers and scientists engaged in the development of magnetic-recording technology are interested in further developing such procedures to control the fly-height of magnetic-recording heads in HDDs upon which the increased recording densities demanded by the marketplace depends.